It is known in the air valve art to provide sliding valve spools for directional flow control air valves, and to mold individual annular end seals on the sliding valve spools, as well as to mold individual annular valve members on the sliding valve spools. A disadvantage of the prior art molded sliding valve spools is that they are not stable, due to side loading. The prior art molded sliding valve spools are provided with annular pressure seal grooves machined in each end of the metal spool body. A disadvantage of such prior art molded sliding valve spools is that the tolerance of the annular pressure seal grooves cannot be held to a close dimension so that the annular pressure seals carried in such machined grooves are stable, so as to resist side loading on the valve spools. U.S. Pat. No. 2,782,801 illustrates a sliding valve spool which has molded annular valve members, and wherein the valve spool is provided with a pair of detachably mounted annular end seal members which are mounted in grooves that are machined around the periphery of the valve spool body. A disadvantage of the sliding valve spool illustrated in the last mentioned patent is that each of the annular end seal members sits in an annular groove which is machined in the valve spool body and which permits the seal to float to a certain extent. The seal has flexibility and it is not possible to hold a very close tolerance of the dimension of the seal groove formed around the periphery of the valve spool by a machining operation, so as to prevent transverse or side loading on the sliding valve spool, whereby the entire sliding valve spool moves transversely or sidewardly, relative to its longitudinal axis, due to side loading.